This invention is in the field of soybean breeding, specifically relating to a soybean variety designated 93B15.
The present invention relates to a new and distinctive soybean variety, designated 93B15 which has been the result of years of careful breeding and selection as part of a soybean breeding program. There are numerous steps in the development of any novel, desirable plant germplasm. Plant breeding begins with the analysis and definition of problems and weaknesses of the current germplasm, the establishment of program goals, and the definition of specific breeding objectives. The next step is selection of germplasm that possess the traits to meet the program goals. The goal is to combine in a single variety an improved combination of desirable traits from the parental germplasm. These important traits may include higher seed yield, resistance to diseases and insects, tolerance to drought and heat, and better agronomic qualities.
Field crops are bred through techniques that take advantage of the plant""s method of pollination. A plant is self-pollinated if pollen from one flower is transferred to the same or another flower of the same plant. A plant is cross-pollinated if the pollen comes from a flower on a different plant. Soybean plants (Glycine max), are recognized to be naturally self-pollinated plants which, while capable of undergoing cross-pollination, rarely do so in nature. Insects are reported by some researchers to carry pollen from one soybean plant to another and it generally is estimated that less than one percent of soybean seed formed in an open planting can be traced to cross-pollination, i.e. less than one percent of soybean seed formed in an open planting is capable of producing F1 hybrid soybean plants, See Jaycox, xe2x80x9cEcological Relationships between Honey Bees and Soybeans, xe2x80x9d appearing in the American Bee Journal Vol. 110(8): 306-307 (August 1970). Thus intervention for control of pollination is critical to establishment of superior varieties.
A cross between two different homozygous lines produces a uniform population of hybrid plants that may be heterozygous for many gene loci. A cross of two plants each heterozygous at a number of gene loci will produce a population of hybrid plants that differ genetically and will not be uniform. Regardless of parentage, plants that have been self-pollinated and selected for type for many generations become homozygous at almost all gene loci and produce a uniform population of true breeding progeny.
Soybeans, (Glycine max), can be bred by both self-pollination and cross-pollination techniques. Choice of breeding or selection methods depends on the mode of plant reproduction, the heritability of the trait(s) being improved, and the type of variety used commercially (e.g., F1 hybrid variety, pureline variety, etc.). For highly heritable traits, a choice of superior individual plants evaluated at a single location will be effective, whereas for traits with low heritability, selection should be based on mean values obtained from replicated evaluations of families of related plants. Popular selection methods commonly include pedigree selection, modified pedigree selection, mass selection, and recurrent selection.
The complexity of inheritance influences choice of the breeding method. Pedigree breeding and recurrent selection breeding methods are used to develop varieties from breeding populations. Pedigree breeding starts with the crossing of two genotypes, each of which may have one or more desirable characteristics that is lacking in the other or which complements the other. If the two original parents do not provide all the desired characteristics, other sources can be included in the breeding population. In the pedigree method, superior plants are selfed and selected in successive generations. In the succeeding generations the heterozygous condition gives way to homogeneous lines as a result of self-pollination and selection. Typically in the pedigree method of breeding five or more generations of selfing and selection is practiced: F1xe2x86x92F2; F2xe2x86x92F3;F3xe2x86x92F4; F4xe2x86x92F5, etc.
Pedigree breeding is commonly used for the improvement of self-pollinating crops. Two parents that possess favorable, complementary traits are crossed to produce an F1. An F2 population is produced by selfing one or several F1""s or by intercrossing two F1""s (sib mating). Selection of the best individuals may begin in the F2 population; then, beginning in the F3, the best individuals in the best families are selected. Replicated testing of families can begin in the F4 generation to improve the effectiveness of selection for traits with low heritability. At an advanced stage of inbreeding (i.e., F6 and F7), the best lines or mixtures of phenotypically similar lines are tested for potential release as new varieties.
Backcross breeding has been used to transfer genes for simply inherited, highly heritable traits into a desirable homozygous variety or inbred line that is utilized as the recurrent parent. The source of the traits to be transferred is called the donor parent. After the initial cross, individuals possessing the desired traits of the donor parent are selected and repeatedly crossed (backcrossed) to the recurrent parent. The resulting plant is expected to have the attributes of the recurrent parent (e.g., variety) and the desirable traits transferred from the donor parent. This approach has been used extensively for breeding disease resistant varieties.
Each soybean breeding program should include a periodic, objective evaluation of the efficiency of the breeding procedure. Evaluation criteria vary depending on the goal and objectives, but should include gain from selection per year based on comparisons to an appropriate standard, overall value of the advanced breeding lines, and number of successful varieties produced per unit of input (e.g., per year, per dollar expended, etc.).
Various recurrent selection techniques are used to improve quantitatively inherited traits controlled by numerous genes. The use of recurrent selection in self-pollinating crops depends on the ease of pollination, the frequency of successful hybrids from each pollination, and the number of hybrid offspring from each successful cross.
Promising advanced breeding lines are thoroughly tested and compared to appropriate standards in environments representative of the commercial target area(s) for three or more years. The best lines are candidates for new commercial varieties; those still deficient in a few traits may be used as parents to produce new populations for further selection.
Publically available or newly-released varieties of soybean can also be used as parental lines or starting materials for breeding or as source populations from which to develop or derive other soybean varieties or breeding lines. These varieties or lines derived from publically available or newly-released varieties can be developed by using breeding methods described earlier, such as pedigree breeding, backcrossing and recurrent selection. As an example, when backcross breeding is used to create these derived lines or varieties in a soybean breeding program, publicly available or newly released varieties of soybeans can be used as a parental line or starting material or source population and can serve as either the donor or recurrent parent. See for example, Fehr, xe2x80x9cBreeding Methods for Cultivar Development xe2x80x9d, Chapter 7, Soybeans Improvement, Production and Uses, 2nd ed., Wilcox ed. 1987.
These processes, which lead to the final step of marketing and distribution, can take from eight to twelve years from the time the first cross is made. Therefore, development of new varieties is a time-consuming process that requires precise forward planning, efficient use of resources, and a minimum of changes in direction.
A most difficult task is the identification of individuals that are genetically superior, because for most traits the true genotypic value is masked by other confounding plant traits or environmental factors. One method of identifying a superior plant is to observe its performance relative to other experimental plants and to a widely grown standard variety. Generally a single observation is inconclusive, so replicated observations are required to provide a better estimate of its genetic worth.
In addition to the preceding problem, it is not known how the genotype will react with the environment. This genotype by environment interaction is an important, yet unpredictable, factor in plant breeding. A breeder of ordinary skill in the art cannot predict the genotype, how that genotype will interact with various environments or the resulting phenotypes of the developing lines, except perhaps in a very broad and general fashion. A breeder of ordinary skill in the art would also be unable to recreate the same line twice from the very same original parents, as the breeder is unable to direct how the genomes combine or how they will interact with the environmental conditions. This unpredictability results in the expenditure of large amounts of research resources in the development of a superior new soybean variety.
The goal of soybean breeding is to develop new, unique and superior soybean varieties. In practical application of a chosen soybean breeding program, the breeder initially selects and crosses two or more parental lines, followed by repeated selfing and selection, producing many new genetic combinations. The breeder can theoretically generate billions of different genetic combinations via crossing, selfing and mutations. The breeder has no direct control at the cellular level. Therefore, two breeders will never develop the same line, or even very similar lines, having the same soybean traits.
Each year, the plant breeder selects the germplasm to advance to the next generation. This germplasm is grown under unique and different geographical, climatic and soil conditions, and further selections are then made during and at the end of the growing season. The varieties which are developed are unpredictable for the reasons already mentioned.
Mass and recurrent selections can be used to improve populations of either self- or cross-pollinated crops. A genetically variable population of heterozygous individuals is either identified or created by intercrossing several different parents. The best plants are selected based on individual superiority, outstanding progeny, or excellent combining ability. The selected plants are intercrossed to produce a new population in which further cycles of selection are continued.
The single-seed descent procedure in the strict sense refers to planting a segregating population, harvesting a sample of one seed per plant, and using the one-seed sample to plant the next generation. When the population has been advanced from the F2 to the desired level of inbreeding, the plants from which lines are derived will each trace to different F2 individuals. The number of plants in a population declines each generation due to failure of some seeds to germinate or some plants to produce at least one seed. As a result, not all of the F2 plants originally sampled in the population will be represented by a progeny when generation advance is completed.
In a multiple-seed procedure, soybean breeders commonly harvest one or more pods from each plant in a population and thresh them together to form a bulk. Part of the bulk is used to plant the next generation and part is put in reserve. The procedure has been referred to as modified single-seed descent or the pod-bulk technique.
The multiple-seed procedure has been used to save labor at harvest. It is considerably faster to thresh pods with a machine than to remove one seed from each by hand for the single-seed procedure. The multiple-seed procedure also makes it possible to plant the same number of seeds of a population each generation of inbreeding. Enough seeds are harvested to make up for those plants that did not germinate or produce seed.
Descriptions of other breeding methods that are commonly used for different traits and crops can be found in one of several reference books (e.g., Allard, 1960; Simmonds, 1979; Sneep et al., 1979; Fehr, 1987).
Proper testing should detect major faults and establish the level of superiority or improvement over current varieties. In addition to showing superior performance, there must be a demand for a new variety. The new variety must be compatible with industry standards, or must create a new market. The introduction of a new variety may incur additional costs to the seed producer, the grower, processor and consumer, for special advertising and marketing, altered seed and commercial production practices, and new product utilization. The testing preceding release of a new variety should take into consideration research and development costs as well as technical superiority of the final variety. For seed-propagated varieties, it must be feasible to produce seed easily and economically.
Soybean (Glycine max), is an important and valuable field crop. Thus, a continuing goal of soybean breeders is to develop stable, high yielding soybean varieties that are agronomically sound. The reasons for this goal are obviously to maximize the amount of grain produced on the land used and to supply food for both animals and humans. To accomplish this goal, the soybean breeder must select and develop soybean plants that have the traits that result in superior varieties.
Pioneer soybean research staff create over 500,000 potential new varieties each year. Of those new varieties, less than 50 and more commonly less than 25 are actually selected for commercial use.
According to the invention, there is provided a novel soybean variety, designated 93B15. This invention thus relates to the seeds of soybean variety 93B15, to the plants of soybean 93B15 and to methods for producing a soybean plant produced by crossing soybean variety 93B15 with itself or another soybean plant, and the creation of variants by mutagenesis or transformation of soybean 93B15. This invention also relates to methods for producing other soybean varieties or breeding lines derived from soybean variety 93B15 and to soybean varieties or breeding lines produced by those methods. Soybean variety 93B15 is characterized by a unique combination of yield potential and disease resistance for its maturity.
In the description and tables which follow, a number of terms are used. In order to provide a clear and consistent understanding of the specification and claims, including the scope to be given such terms, the following definitions are provided:
B/A=BUSHELS PER ACRE. The seed yield in bushels/acre is the actual yield of the grain at harvest.
BSR=BROWN STEM ROT TOLERANCE. This is a visual disease score from 1 to 9 comparing all genotypes in a given test. The score is based on leaf symptoms of yellowing and necrosis caused by brown stem rot. A score of 9 indicates no symptoms. Visual scores range down to a score of 1 which indicates severe symptoms of leaf yellowing and necrosis.
CNKR=STEM CANKER TOLERANCE. This is a visual disease score from 1 to 9 comparing all genotypes in a given test. The score is based upon premature plant death. A score of 9 indicates no symptoms, whereas a score of 1 indicates the entire experimental unit died very early.
COTYLEDON. A cotyledon is a type of seed leaf. The cotyledon contains the food storage tissues of the seed.
EMBRYO. The embryo is the small plant contained within a mature seed.
F3. This symbol denotes a generation resulting from the selfing of the F2 generation along with selection for type and rogueing of off-types. The xe2x80x9cF xe2x80x9d number is a term commonly used in genetics, and designates the number of the filial generation. The xe2x80x9cF3xe2x80x9d generation denotes the offspring resulting from the selfing or self mating of members of the generation having the next lower xe2x80x9cF xe2x80x9d number, viz. the F2 generation.
FECL=IRON-DEFICIENCY CHLOROSIS. Plants are scored 1 to 9 based on visual observations. A score of 1 indicates the plants are dead or dying from iron- deficiency chlorosis, a score of 5 means plants have intermediate health with some leaf yellowing and a score of 9 means no stunting of the plants or yellowing of the leaves.
FEY=Frogeye Tolerance. This is a visual disease score from 1 to 9 comparing all genotypes in a given test. The score is based upon leaf lesions. A score of 9 indicates no lesions, whereas a score of 1 indicates severe leaf necrosis.
HABIT. This refers to the physical appearance of a plant. It can be either determinate or indeterminate. In soybeans, indeterminate varieties are those in which stem growth is not limited by formation of a reproductive structure (i.e., flowers, pods and seeds) and hence growth continues throughout flowering and during part of pod filling. The main stem will develop and set pods over a prolonged period under favorable conditions. In soybeans, determinate varieties are those in which stem growth ceases at flowering time. Most flowers develop simultaneously, and most pods fill at approximately the same time.
HGT=Plant Height. Plant height is taken from the top of the soil to top pod of the plant and is measured in inches.
HILUM. This refers to the scar left on the seed which marks the place where the seed was attached to the pod prior to it (the seed) being harvested.
HYPL=HYPOCOTYL ELONGATION. This score indicates the ability of the seed to emerge when planted 3xe2x80x3 deep in sand and with a controlled temperature of 25xc2x0 C. The number of plants that emerge each day are counted. Based on this data, each genotype is given a 1 to 9 score based on its rate of emergence and percent of emergence. A score of 9 indicates an excellent rate and percent of emergence, an intermediate score of 5 indicates average ratings and a 1 score indicates a very poor rate and percent of emergence.
HYPOCOTYL. A hypocotyl is the portion of an embryo or seedling between the cotyledons and the root. Therefore, it can be considered a transition zone between shoot and root.
LDG=LODGING RESISTANCE. Lodging is rated on a scale of 1 to 9. A score of 9 indicates erect plants. A score of 5 indicates plants are leaning at a 45xc2x0 angle in relation to the ground and a score of 1 indicates plants are laying on the ground.
LEAFLETS. These are part of the plant shoot, and they manufacture food for the plant by the process of photosynthesis.
LLE=Linoleic Acid Percent. Linoleic acid is one of the five most abundant fatty acids in soybean seeds. It is measured by gas chromatography and is reported as a percent of the total oil content.
LLN=Linolenic Acid Percent. Linolenic acid is one of the five most abundant fatty acids in soybean seeds. It is measured by gas chromatography and is reported as a percent of the total oil content.
MAT ABS=ABSOLUTE MATURITY. This term is defined as the length of time from planting to complete physiological development (maturity). The period from planting until maturity is reached is measured in days, usually in comparison to one or more standard varieties. Plants are considered mature when 95% of the pods have reached their mature color.
MATURITY GROUP. This refers to an agreed-on industry division of groups of varieties, based on the zones in which they are adapted primarily according to day length or latitude. They consist of very long day length varieties (Groups 000, 00, 0), and extend to very short day length varieties (Groups VII, VIII, IX, X).
OIL=Oil Percent. Soybean seeds contain a considerable amount of oil. Oil is measured by NIR spectrophotometry, and is reported on an as is percentage basis.
OLC=OLEIC ACID PERCENT. Oleic acid is one of the five most abundant fatty acids in soybean seeds. It is measured by gas chromatography and is reported as a percent of the total oil content.
PLM=Palmitic Acid Percent. Palmitic acid is one of the five most abundant fatty acids in soybean seeds. It is measured by gas chromatography and is reported as a percent of the total oil content.
POD. This refers to the fruit of a soybean plant. It consists of the hull or shell (pericarp) and the soybean seeds.
PRT=PHYTOPHTHORA TOLERANCE. Tolerance to Phytophthora root rot is rated on a scale of 1 to 9, with a score of 9 being the best or highest tolerance ranging down to a score of 1 which indicates the plants have no tolerance to Phytophthora.
PRM=Predicted Relative Maturity. Soybean maturities are divided into relative maturity groups. In the United States the most common maturity groups are 0 through VIII. Within these maturity groups the industry generally divides maturities into tenths of a relative maturity group. Within narrow comparisons, the difference of a tenth of a relative maturity group equates very roughly to a day difference in maturity at harvest.
PRO=Protein Percent. Soybean seeds contain a considerable amount of protein. Protein is generally measured by NIR spectrophotometry, and is reported on an as is percentage basis.
PUBESCENCE. This refers to a covering of very fine hairs closely arranged on the leaves, stems and pods of the soybean plant.
RKA=Root-knot nematode, peanut. This is a visual disease score from 1 to 9 comparing all genotypes in a given test. The score is based upon digging plants to look at the roots for presence or absence of galling. A score of 9 indicates that there is no galling of the roots, a score of 1 indicates large severe galling cover most of the root system which results in pre-mature death from decomposing of the root system.
RKI=Root-knot nematode, southern. This is a visual disease score from 1 to 9 comparing all genotypes in a given test. The score is based upon digging plants to visually score the for presence or absence of galling. A score of 9indicates that there is no galling of the roots, a score of 1 indicates large severe galling cover most of the root system which results in pre-mature death from decomposing of the root system.
SDS=Sudden Death Syndrome. Tolerance to Sudden Death Syndrome is rated on a scale of 1 to 9, with a score of 1 being very susceptible ranging up to a score of 9 being resistant.
S/LB=Seeds per Pound. Soybean seeds vary in seed size, therefore, the number of seeds required to make up one pound also varies. This affects the pounds of seed required to plant a given area, and can also impact end uses.
SH=SHATTERING. This refers to the amount of pod dehiscence prior to harvest. Pod dehiscence involves seeds falling from the pods to the soil. This is a visual score from 1 to 9 comparing all genotypes within a given test. A score of 9 means pods have not opened and no seeds have fallen out. A score of 5 indicates approximately 50% of the pods have opened, with seeds falling to the ground and a score of 1 indicates 100% of the pods are opened.
SHOOTS. These are a portion of the body of the plant. They consist of stems, petioles and leaves.
STC=STEARIC ACID PERCENT. Stearic acid is one of the five most abundant fatty acids in soybean seeds. It is measured by gas chromatography and is reported as a percent of the total oil content.
WH MD=WHITE MOLD TOLERANCE. This is a visual disease score from 1 to 9 comparing all genotypes in a given test. The score is based upon observations of mycelial growth and death of plants. A score of 9 indicates no symptoms. Visual scores of 1 indicate complete death of the experimental unit.